The present invention relates to a front-wheel drive control device in a four-wheel driven vehicle.
There is known a four-wheel driven vehicle such as an agricultural tractor travelling with two front-wheels and two rear-wheels all driven. Such vehicle is highly efficient in travelling on a rough field such as a rice field, but is disadvantageously turned with a large turning radius. Provision is therefore made such that a high/low speed changeover device in the front wheel driving system is switched to the high speed side at the time of turning, thereby to increase the front wheel peripheral speed to 2-3 times the straight travelling speed, thus decreasing the turning radius. Such changeover is made manually or automatically upon detection of the steering wheel turning angle. Accordingly, such changeover is either troublesome for the former case or attended with danger for the latter case, because the turning radius is uniformly reduced even if the vehicle travels at such high speed that reduction in turning radius involves some risk.